Cell Signalling lecture 1 ionic gradients and how they're established + voltage gated channels

Question 1

What are the three regulatory proteins?

Answer 1

metabolic enzyme (altered metabolism), gene regulatory protein (altered gene expression), cytoskeletal protein (altered cell shape or movement)

Question 2

What can calcium signalling lead to ? (time domain)

Answer 2

gene transcription(min), metabolism(s), exocytosis (microseconds), contraction(ms), fertilisation(hr), proliferation(hr), hypertrophy (hr)

Question 3

What is proliferation ?

Answer 3

Cell proliferation is the process that results in an increase of the number of cells, and is defined by the balance between cell divisions and cell loss through cell death or differentiation. Cell proliferation is increased in tumours.

Question 4

What is hypertrophy ?

Answer 4

the enlargement of an organ or tissue from the increase in size of its cells.

Question 5

Conc of Na+? mM

Answer 5

Intracellular 5-15

Extracellular 145

Question 6

Conc of K+ ? Mm

Answer 6

Intracellular 140

Extracellular 5

Question 7

Conc of Mg 2+ ? Mm

Answer 7

Intracellular 0.5

Extracellular 1-2

Question 8

Conc Ca2+ ? Mm

Answer 8

Intracellular 10^-4

Extracellular 1-2

Question 9

Conc of H+ ? Mm

Answer 9

Intracellular 7*10^-5 (10^-7.2M, pH 7.2)

Extracellular 4*10^-5 (10^-7.4M or pH7.4)

Question 10

Conc of Cl-? Mm

Answer 10

Intracellular 5-15

Extracellular 110

Question 11

What is the conc of Ca2+ in the ER?

Answer 11

0.5 mM

Question 12

What is the approximate pH in lysosomes ?

Answer 12

4.5

Question 13

What is the approximate pH in mitochondria ?

Answer 13

7.8

Question 14

What does primary active transport require ?

Answer 14

ATP + H20 releasing energy and a phosphate ion

Question 15

What type is the Na+/k+ pump ?

Answer 15

p-type ATPase

Question 16

Describe the mechanism of the Na+/k+ pump ?

Answer 16

3Na+ bound 
ATP to ADP Phosphate group bound to pump
3Na+ out
2K+ bound phosphate group still bound
phosphate group released 
2 K+ in

Question 17

How does calcium ionic gradient across the cell membrane established
?

Answer 17

PMCA which is a P-type ATPase pumps calcium out of the cell

Question 18

How is the ionic gradient between the cytosol and the endoplasmic reticulum established ?

Answer 18

by SERCA which is a p-type ATPase that pumps calcium into the ER

Question 19

What type of porter is the Na+/ca2+ exchanger ? how many transmembrane regions does the exchanger exhibit ?

Answer 19

Antiporter 3Na+ in down electrochemical gradient 2Ca2+ out against electrochemical gradient. 9

Question 20

So how are ionic gradients established ?

Answer 20

by primary active transport and secondary transport (exchanger) ex na-k pump, pmca , serca which are all P-type ATPases, Na+/Ca2+ exchanger

Question 21

How many transmembrane domains do K+ voltage gated ion channels exhibit ? how about Na+ or Ca2+?

Answer 21

6. 4 (tetrameric) of which are voltage sensing domains. and 2 are pore domains. - 24

Question 22

Why can’t Na+ pass down K+ ion channels ?

Answer 22

because the selectivity filter in the pore domain stabilises the larger dehydrated K+ ion by forming 4 electrostatic charges between O and K. Na+ only needs 2 electrostatic charges to be stabilised therefore it is rejected.

Question 23

How is voltage sensed in voltage gated ion channels?

Answer 23

by positively charged residues in the S4 region. Regulary spaced arginine (R) and lysine (K) residues ‘sense’ potential changes which mediate a conformational change - s4 region pops up opening the ion channel